Anmol Sidhu

Control Strategies for a Roll Simulator for Recreational Off-Highway Vehicles

Control strategies for a two degree-of-freedom roll simulator are presented. The simulator consists of a sled-platform assembly that translates along rails. A Recreational Off-Highway Vehicle (ROV) is mounted on the platform, which has the freedom to rotate about a roll axis. The roll axis is nominally perpendicular to the rails and parallel to the ground plane. This can be altered by using the third degree-of-freedom (static) that yaws the platform and changes the angle of the roll axis with respect to the rails. This angle is incorporated to achieve the appropriate acceleration vector. The assembly accelerates to a desired speed via a hydraulic motor and is decelerated with a magnetic particle brake at a specified deceleration level (nominally 0.7 g). Coordination of two mechanical systems proved to be difficult due to inherent lags in both systems. The cable-drum system created many problems as tension needs to be maintained in the cable at all times. Using only knowledge of the physical system, results showed reasonable agreement with desired levels. The roll motions showed excellent correlation with the desired levels.Copyright

Portable Automated Driver for Road Vehicle Dynamics Testing

An automated test driver (ATD) has been developed which is capable of executing dynamic test maneuvers with accuracy and repeatability beyond the ability of a human driver. This system enables any production car or light truck to follow a user-defined path or to perform specific steering sequences with excellent repeatability. Combined with an automated brake and throttle controller, capable of matching a desired velocity profile as well as providing specific test inputs with acceleration or other feedback, this system provides a powerful tool to improve vehicle dynamics testing.Copyright

Modeling and Validation of a Roll Simulator for Recreational Off-Highway Vehicles

A model of a roll simulator for recreational off-highway vehicles (ROV) is presented. Models of each sub-system are described including the equations of motion, the braking, hydraulic and roll motor systems. Derivation of the equations of motion, obtained using Lagrange’s energy equation, demonstrates that they have three degrees-of-freedom (two dynamic, one static) and are coupled and highly non-linear. Results from the hydraulic sub-system illustrated that the amount of entrapped air in the system can significantly influence the response. Comparisons of the model with experimental data from the actual roll simulator showed close agreement. The greatest difference was with motor pressure. The acceleration levels and roll motions for both the model and experimental data showed excellent correlation.Copyright

Model Based Study of Stability Limits for Three Wheeled Vehicles Using ADAMS/Car

Three-wheeled motor vehicles have been around for close to a half a century now, but they have largely remained in the realm of recreational or concept vehicles. Due to increasing fuel prices and an emphasis on fuel efficient design, the automotive industry is exploring the three-wheeled option now more than ever as a mainstream daily-use vehicle. The trend is evident from the Automotive X-Prize which featured six teams with three-wheeled vehicle designs to meet the fuel efficiency target [1]. A three-wheeled vehicle design offers vast potential for improvement in overall fuel efficiency over their four wheeled counterparts, as it lends itself to a tear-drop shape which is highly aerodynamic and is also likely to be lighter and have lower rolling resistance. These factors have considerable impact on improving fuel efficiency, but such a design also presents challenges in terms of vehicle stability and can be susceptible to roll-over or spin out in certain scenarios. The primary factor that determines the stability of a three-wheeled vehicle is its center of gravity (CG). This paper uses a model-based approach to explore the CG position limits for stable operation of a front wheel drive three wheel vehicle and aims to give an empirical basis for deciding CG position limits for future three wheel vehicle design. ADAMS/Car is used to model the vehicle and the model is validated using test data from a commercially available three-wheeled vehicle. The performance of the model is then studied for various CG positions and the limits of safe operation are established for this particular model.Copyright